[PATCH] D106053: [CodeGen] Remove pending AssertZext AssertSext in promoting FP_TO_INT

Fri Jul 16 19:12:41 PDT 2021

xiangzhangllvm added a comment.

In D106053#2885026 <https://reviews.llvm.org/D106053#2885026>, @efriedma wrote:

>> +  After appending AssertZext, the shuffle optimization will stop zero these elements, and directly use them.   That is wrong.
>
> I agree up to this point.
>
> The question is, is the AssertZext node wrong, or are the shuffle optimizations wrong?  That dictates whether we go with this patch, or instead revert 2a419a0b9957 <https://reviews.llvm.org/rG2a419a0b9957ebac9e11e4b43bc9fbe42a9207df> (and any similar optimizations, if they exist).

It is the "adding AssertZext node" wrong. AssertZext node should correctly marked node which is really zero in N bits.

> In any case, we should probably add the following example as a regression test:
> ...

No problem, Let me add the test soon, thanks you!

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D106053/new/

https://reviews.llvm.org/D106053